CN114423832A

CN114423832A - Coating compositions comprising zirconium dioxide pigment particles

Info

Publication number: CN114423832A
Application number: CN202080064891.0A
Authority: CN
Inventors: A·埃尔顿-勒格里; A·普利斯; P·卡托尔尼格; H·多拉尼; M·潘特林
Original assignee: Imesche
Current assignee: Imesche
Priority date: 2019-09-20
Filing date: 2020-09-18
Publication date: 2022-04-29
Also published as: EP3795644A1; EP4031628A1; WO2021053145A1

Abstract

The invention relates to a coating composition comprising pigment particles, wherein the median particle diameter d of the pigment particles, measured by sedimentation using a Sedigraph₅₀From about 0.1 μm to about 5 μm, and the pigment particles comprise: i) at least about 70% by weight zirconium dioxide; ii) up to 15 wt% silica; iii) from about 0.1 to about 15 weight percent of one or more metal oxides selected from the group consisting of magnesium oxide, calcium oxide, yttrium oxide, scandium oxide, hafnium oxide, ytterbium oxide, aluminum oxide, and cerium oxide; and iv) at least about 97 weight percent of a combination of i), ii), and iii), wherein the weight percent of zirconium dioxide of i) is the equivalent weight percent zirconium dioxide as determined by XRF; weight percent of silica of ii)The ratio is the equivalent silica weight percent as determined by XRF; the weight percent of the one or more metal oxides of iii) is the equivalent weight percent of the one or more metal oxides as determined by XRF; and wherein the weight percentages of i), ii), iii) and iv) are each based on the total weight of the pigment particles. The invention also relates to the use of the coating composition herein and to a process for its preparation.

Description

Coating compositions comprising zirconium dioxide pigment particles

Technical Field

The invention relates to a coating composition comprising pigment particles, wherein the median particle diameter d of the pigment particles, measured by sedimentation using a Sedigraph₅₀From about 0.1 μm to about 5 μm, and comprises: i) at least about 70% by weight zirconium dioxide; ii) up to about 15 wt% silica; iii) from about 0.1% to about 15% by weight of one or more metal oxides selected from the group consisting of magnesium oxide, calcium oxide, yttrium oxide, scandium oxide, hafnium oxide, ytterbium oxide, aluminum oxide, and cerium oxide; iv) at least about 97% by weight of a combination of i), ii) and iii), wherein the weight percent of zirconium dioxide of i) is the equivalent weight percent zirconium dioxide as determined by XRF; the weight percent of silica of ii) is the equivalent weight percent silica as determined by XRF; the weight percent of the one or more metal oxides of iii) is the weight percent of the equivalent weight of the one or more metal oxides as determined by XRF; and wherein the weight percentages of i), ii), iii) and iv) are each based on the total weight of the pigment particles. The invention also relates to the use of the coating composition herein and to a process for its preparation.

Background

The coating composition is applied to a substrate to form a solid thin film upon drying to color, cover and protect an object. In its components, the coating composition comprises a pigment, wherein a solid substance is dispersed throughout the coating to impart color and/or opacity. Pigments can protect the substrate from uv light and can also alter appearance (e.g., gloss) and other properties (e.g., hardness and ductility).

The most common white pigment used in coatings to achieve dry and wet opacity is titanium dioxide because of its whiteness and high refractive index. However, it is now desirable to produce coating compositions that are substantially free of titanium dioxide. This is due to the expense and perceived environmental impact of titanium dioxide. Coating compositions having low titanium dioxide or substantially no titanium dioxide generally have low opacity compared to coating compositions comprising substantial amounts of titanium dioxide.

Other white minerals have a high refractive index and can be used as a substitute for titanium dioxide in terms of aesthetic properties. For example, the refractive index of zinc oxide is relatively high, 2.1. However, zinc oxide is not suitable for use in coating compositions because certain jurisdictions do not allow for levels in excess of 500ppm for health and safety reasons. Zinc sulfide has a high refractive index of about 2.4 and is also not suitable due to health and safety issues, such as its role as a skin and respiratory sensitizer. Accordingly, there is a need to provide alternative pigments to titanium dioxide in coating compositions that provide good aesthetic characteristics while avoiding the environmental impact associated with titanium dioxide.

Disclosure of Invention

The invention is defined in the appended claims.

According to a first aspect, there is provided a coating composition comprising pigment particles, wherein the pigment particles have a median particle diameter d50, measured by sedimentation using a Sedigraph, of from about 0.1 μm to about 5 μm, and the pigment particles comprise:

ii) at least about 70 weight percent zirconium dioxide;

ii) up to about 15 wt% silica;

iii) from about 0.1% to about 15% by weight of one or more metal oxides selected from the group consisting of magnesium oxide, calcium oxide, yttrium oxide, scandium oxide, hafnium oxide, ytterbium oxide, aluminum oxide, and cerium oxide; and

iv) at least about 97% by weight of a combination of i), ii) and iii),

wherein the weight percent of zirconium dioxide of i) is the equivalent weight percent zirconium dioxide as determined by XRF; the weight percent of silica of ii) is the equivalent weight percent silica as determined by XRF; the weight percent of the one or more metal oxides of iii) is the equivalent weight percent of the one or more metal oxides as determined by XRF; and wherein the weight percentages of i), ii), iii) and iv) are each based on the total weight of the pigment particles.

According to a second aspect, there is provided a method of preparing a coating composition according to the first aspect, comprising blending pigment particles with other components of the coating composition.

According to a third aspect, there is provided the use of a coating composition according to the first aspect for coating an article or substrate.

According to a fourth aspect, there is provided a method of coating an article or substrate comprising coating the article or substrate with a coating composition according to the first aspect.

According to a fifth aspect, there is provided an article or substrate coated with a coating composition according to the first aspect.

Certain embodiments of the invention may provide one or more of the following advantages:

desired paint aesthetic properties, such as wet opacity;

desired paint aesthetic properties, such as dry opacity;

desired paint aesthetic properties, such as gloss;

desired paint aesthetic properties, such as brightness;

desired physical properties of the coating, such as hardness;

desired physical properties of the coating, such as scrub resistance;

desired physical properties of the coating, such as crack resistance;

the desired non-toxicity.

The details, examples and preferences provided in connection with any particular one or more of the described aspects of the invention are equally applicable to all aspects of the invention. Any combination of the embodiments, examples and preferred versions described herein is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Detailed Description

The present invention is based on the following findings: the optimized zirconium dioxide can be used in coating compositions to provide good aesthetic properties, such as providing good coverage and opacity.

Zirconium dioxide, ZrO₂Also known as zirconia, is a white crystalline oxide of zirconium. Naturally occurring zirconium dioxide exists predominantly in the form of monoclinic crystal structure, which is the expected structure at temperatures below 1170 ℃. Zirconium dioxide is present in tetragonal form at temperatures between 1170 ℃ and 2370 ℃ and in cubic form at temperatures above 2370 ℃. Zirconia can also be produced by known methods, such as calcining zirconium compounds. At ZrO₂Contains yttrium oxide (Y)₂O₃) Can be used to stabilize such structures in cubic form at temperatures below 2370 deg.C.

Unless otherwise indicated, "weight percent" as disclosed and used herein is the equivalent weight percent as determined by XRF. For example, the weight percent of zirconium disclosed herein is the equivalent weight percent of zirconium dioxide as determined by XRF, and the weight percent of the one or more metal oxides is the equivalent weight percent of the one or more metal oxides as determined by XRF. The weight percentage is determined by chemical analysis of the refractory product using X-ray fluorescence (XRF) -fused cast beads method (ISO 12677: 2011).

Pigment particle composition

According to any of the embodiments of the present disclosure described herein, the pigment particles of the present disclosure comprise, consist of, or consist essentially of at least about 70 weight percent zirconium dioxide, based on the total weight of the pigment particles. In certain embodiments, the pigment particles may comprise at least about 75 wt.%, or at least about 78 wt.%, at least about 80 wt.%, at least about 85 wt.%, or at least about 87 wt.%, or at least about 90 wt.%, or at least about 92 wt.%, or at least about 95 wt.%, or at least about 96 wt.%, or at least about 97 wt.%, or at least about 98 wt.%, or at least about 99 wt.%, or at least about 99.5 wt.% zirconium dioxide, based on the total weight of the pigment particles.

The pigment particles of the present invention also comprise up to about 15 weight percent silica, based on the total weight of the pigment particle. For example, the pigment particles may comprise up to about 14 wt% silica, or up to about 13 wt% silica, or up to about 12 wt% silica, or up to about 11 wt% silica, or up to about 10 wt% silica, or up to about 9 wt% silica, or up to about 8 wt% silica, or up to about 7 wt% silica, or up to about 6 wt% silica, or up to about 5 wt% silica, or up to about 4 wt% silica, or up to about 3 wt% silica, or up to about 2 wt% silica, or up to about 1 wt% silica, or at least about 0.1 wt% silica, or at least about 0.2 wt% silica, or about 0.1 wt% to about 10 wt% silica, based on the total weight of the pigment particle, Or from about 0.1 wt% to about 7 wt% silica, or from about 0.2 wt% to about 5 wt% silica, or from about 0.2 wt% to about 3 wt% silica.

The pigment particles of the present invention further comprise one or more metal oxides in an amount of from about 0.1 weight percent to about 15 weight percent, based on the total weight of the pigment particles. In certain embodiments, the pigment particles may comprise one or more metal oxides in an amount of from about 0.2 wt% to about 14 wt%, or from about 0.3 wt% to about 13 wt%, or from about 0.5 wt% to about 12 wt%, or from about 0.7 wt% to about 11 wt%, or from about 1 wt% to about 10 wt%, or from about 1.5 wt% to about 9 wt%, or from about 2 wt% to about 8 wt%, or from about 3 wt% to about 7 wt%, or from about 4 wt% to about 6 wt%, based on the total weight of the pigment particles.

In certain embodiments, the metal oxide comprises, consists of, or consists essentially of an oxide selected from the group consisting of magnesium oxide, calcium oxide, yttrium oxide, scandium oxide, hafnium oxide, ytterbium oxide, aluminum oxide, and cerium oxide, and combinations thereof. In one example embodiment, the pigment particles can comprise, consist of, or consist essentially of zirconium dioxide and hafnium dioxide. In another example, the pigment particles can comprise, consist of, or consist essentially of zirconium dioxide, hafnium dioxide, and yttrium oxide.

In certain embodiments, the pigment particles may comprise from about 0.01 wt% to about 2.5 wt% hafnium oxide, or from about 0.05 wt% to about 2.0 wt% hafnium oxide, or from about 0.1 wt% to about 1.5 wt% hafnium oxide, or from about 0.5 wt% to about 1.0 wt% hafnium oxide, or from about 0.6 wt% to about 0.8 wt% hafnium oxide, or from about 0.1 wt% to about 0.3 wt% hafnium oxide, or from about 1.5 wt% to about 2.0 wt% hafnium oxide, based on the total weight of the pigment particles.

In certain embodiments, the pigment particles can comprise about 0.01% to about 14.99% by weight yttrium dioxide, or about 0.05% to about 14.5% by weight yttrium dioxide, or about 0.1% to about 14% by weight yttrium dioxide, or about 0.5% to about 13% by weight yttrium dioxide, or about 1% to about 12% by weight yttrium dioxide, or about 2% to about 11% by weight yttrium dioxide, or about 3% to about 10% by weight yttrium dioxide, or about 4% to about 9% by weight yttrium dioxide, or about 5% to about 8% by weight yttrium dioxide, or about 6% to about 7% by weight yttrium dioxide, based on the total weight of the pigment particle. In one example, the pigment particles comprise monoclinic zirconia and up to about 2 percent by weight of yttrium dioxide, based on the total weight of the pigment particles. In one example, the pigment particles comprise stabilized zirconium dioxide and up to about 5 weight percent yttrium dioxide, based on the total weight of the pigment particles. An yttrium dioxide content of about 5 wt.% can provide partial stabilization of the cubic structure. In one example, the pigment particles comprise stabilized zirconium dioxide and up to about 12 weight percent yttrium dioxide, based on the total weight of the pigment particles. An yttrium dioxide content of about 12% by weight can provide complete or substantially complete stabilization of the cubic structure.

In certain embodiments, the pigment particles comprise less than about 0.05 wt% iron oxide, based on the total weight of the pigment particles, as determined by XRF. For example, the pigment particles may comprise less than about 0.04 wt% iron oxide, or less than about 0.03 wt% iron oxide, or less than about 0.02 wt% iron oxide, or less than about 0.01 wt% iron oxide, based on the total weight of the pigment particles, as determined by XRF.

The pigment particles comprise zirconium dioxide according to the invention and one or more metal oxides according to the invention, the combined weight being at least about 97 wt.%, or at least about 97.5 wt.%, or at least about 98 wt.%, or at least about 98.5 wt.%, or at least about 99 wt.%, or at least about 99.5 wt.%, or at least about 99.9 wt.%, based on the total weight of the pigment particles.

In certain embodiments, at least a portion of the zirconium dioxide and at least a portion of the one or more metal oxides can be present in the pigment particles as a mixture. In such mixtures, the zirconium dioxide and the metal oxide combine to form pigment particles, wherein each component remains distinct.

In certain embodiments, at least a portion of the zirconium dioxide and at least a portion of the one or more metal oxides can be present in the pigment particles as components of a metal oxide structure. In the metal oxide structure, zirconium dioxide and one or more metal oxides form a monolithic structure in which the components are not each different. In certain embodiments, the metal oxide structure may be a crystalline structure. In certain embodiments, the metal oxide structure may be monoclinic, tetragonal, cubic, or a mixture thereof. In certain embodiments, the metal oxide may be monoclinic. In certain embodiments, the metal oxide structure can be monoclinic and comprises at least about 97% by weight zirconium dioxide, as determined by XRF, based on the total weight of the pigment particles. In certain embodiments, the metal oxide structures may be monoclinic and comprise at least about 97.5 wt.% zirconium dioxide, or may be monoclinic and comprise at least about 98 wt.% zirconium dioxide, or be monoclinic and comprise at least about 98.5 wt.% zirconium dioxide, or be monoclinic and comprise at least about 99 wt.% zirconium dioxide, or be monoclinic and comprise at least about 99.5 wt.% zirconium dioxide (based on the total weight of the pigment particles). In certain embodiments, the metal oxide may be tetragonal. In certain embodiments, the metal oxide may be cubic.

Particle size

The pigment particles of the present invention have a median particle diameter d of from about 0.1 μm to about 5 μm, measured according to the Sedigraph method₅₀. In certain embodiments, the pigment particles can have a median particle diameter d, measured according to the Sedigraph method, of from about 0.1 μm to about 1 μm, or from about 0.15 μm to about 1 μm, or from about 0.2 μm to about 0.8 μm, or from about 0.2 μm to about 0.6 μm, or from about 0.3 μm to about 0.5 μm₅₀. In certain embodiments, the pigment particles can have a median particle diameter d from about 0.15 μm to about 5.0 μm, or from about 0.25 μm to about 4.5 μm, or from about 0.3 μm to about 4.0 μm, or from about 0.35 μm to about 3.5 μm, or from about 0.4 μm to about 3.0 μm, or from about 0.5 μm to about 2.5 μm, or from about 0.6 μm to about 2.0 μm, or from about 0.8 μm to about 1.5 μm, measured according to the Sedigraph method₅₀. In certain embodiments, the pigment particles can have a median particle diameter d from about 1.0 μm to about 5.0 μm, or from about 1.05 μm to about 4.5 μm, or from about 1.3 μm to about 4.0 μm, or from about 1.3 μm to about 3.5 μm, or from about 1.4 μm to about 3.0 μm, or from about 1.4 μm to about 2.5 μm, or from about 1.7 μm to about 3.5 μm, or from about 2.0 μm to about 3.0 μm, or from about 2.3 μm to about 2.7 μm, measured according to the Sedigraph method₅₀. In certain embodiments, the pigment particles may have a particle size of at most about 5.0 μm, or at most about 4.8 μm, or at most about 4.6 μm, or at most about 4.4 μm, or at most about 4.2 μm, 4.0 μm, or at most about 3.8 μm, or at most about 3.6 μm, or at most about 3.4 μm, or at most about 3.2 μm, 3.0 μm, or at most about 2.8 μm, or at most about 2.6 μm, or at most about 2.4 μm, or at most about 2.2 μm, 2.0 μm, or at most about 1.8 μm, or at most about 1.6 μm, or at most about 1.4 μm, or at most about 1.2 μm, or measured according to the Sedigraph methodA median particle diameter d of at most about 1.0 μm, or at most about 0.8 μm, or at most about 0.6 μm, or at most about 0.4 μm₅₀. In certain embodiments, the pigment particles may have a median particle diameter d of at least about 0.10 μm or at least about 0.12 μm, or at least about 0.17 μm, or at least about 0.22 μm, or at least about 0.27 μm, or at least about 0.32 μm, or at least about 0.37 μm₅₀. In certain embodiments, the pigment particles may have a median particle diameter d of at most about 0.52 μm, or at most about 0.57 μm, or at most about 0.62 μm, or at most about 0.67 μm, or at most about 0.72 μm, at most about 0.77 μm, or at most about 1.0 μm, or at most about 1.05 μm, as measured according to the Sedigraph method₅₀。

In certain embodiments, having a median particle diameter, d, of greater than about 1.0 μm to about 5.0 μm₅₀The pigment particles of (a) do not require a wet milling or wet milling step and can be obtained using dry milling. The use of dry milling rather than wet or wet milling may be associated with reduced costs. In addition, grinding particles having a larger median particle size may be more likely than grinding smaller particles (i.e., median particle size d)₅₀Particles below about 1.0 μm) require less energy, which can also be used to reduce costs. In certain embodiments, larger particles (i.e., median particle diameter d) are observed₅₀Particles equal to or greater than about 1.0 μm) is increased.

The median equivalent particle diameter (d) of the pigment particles mentioned herein₅₀Values) and other particle size characteristics are measured by one of two methods in a well-known manner. One method involves the following measurements, which are made in a well-known manner: a Sedigraph5100 instrument supplied by Micromeritics Instruments Corporation of Norcross, Georgia, USA, referred to herein as the "Micromeritics Sedigraph5100 unit" (Phone: + 17706623620; website:www.micromeritics.com) Measured by allowing the particulate material to settle under conditions of complete dispersion in an aqueous medium. This instrument gives a plot of the measured values and cumulative weight percent of particles having a size less than the given esd value, which is known in the art as the "equivalent spherical diameter" (esd). Median particle diameter d₅₀Is the value of the particles esd determined in such a way that 50% by weight thereof% of the particles having a d of less than₅₀Equivalent spherical diameter of value. Another method involves measurement by laser light scattering using a Malvern Mastersizer S instrument such as that supplied by Malvern Instruments Ltd (or by other methods that give essentially the same results). In laser scattering techniques, the particle size in powders, suspensions and emulsions can be measured using diffraction of a laser beam based on the application of mie theory.

In certain embodiments, the brightness of the pigment particles can be at least 85 (measured according to ISO 2470-2 using a D65 light source). For example, the brightness of the pigment particles measured according to ISO 2470-2 may be at least 87, or at least 90, or at least 92, or at least 95, or at least 97.

Coating composition

In certain embodiments, the pigment particles may be present in the coating composition in an amount of from about 1 wt% to about 10 wt%, or from about 1 wt% to about 8 wt%, or from about 1 wt% to about 6 wt%, or from about 2 wt% to about 9 wt%, or from 3 wt% to about 7 wt%, or from about 4 wt% to about 5 wt%, based on the total weight of the coating composition.

In certain embodiments, the coating composition is measured at 8m according to ISO6504-3²The dry opacity can be at least 95%. For example, the coating composition is measured at 8m according to ISO6504-3²The dry opacity may be at least 96%, or at least 97%, or at least 98%, or at least 99%.

In certain embodiments, the coating composition is at 8m²The wet opacity may be at least 75%. Wet opacity was measured according to ISO6504-3 modified to omit the final drying step. For example, the coating composition measured according to ISO6504-3 modified to omit the final drying step is at 8m²The wet opacity may be at least 77%, or at least 80%, or at least 82%, or at least 85%, or at least 87%, or at least 90%, or at least 92%, or at least 95%, or at least 97%, or at least 99%.

In certain embodiments, the dry opacity according to ISO6504-3 is usedCoating composition at 8m measured by CIE whiteness index L²The whiteness per liter can be at least 95%. For example, the coating composition is measured at 8m according to ISO6504-3²The CIE whiteness of/l can be at least 95.5, or at least 95.7, or at least 96, or at least 96.2, or at least 97, or at least 97.5, or at least 98, or at least 98.5, or at least 99, or at least 99.5.

The coating composition according to the invention may comprise resins, such as polymeric or oligomeric resins, defoamers (also known as suds suppressors), crosslinkers, dispersants (also known as diffusants), coalescents, adhesion promoters, wetting agents, rheology agents, light stabilizers and/or uv absorbers. For example, the polymer resin may be suitable for forming a homopolymer or a copolymer. Suitable examples include polyacrylates, polyesters, polyamides, polyurethanes, polyimides, polyureas, polyethers, polysiloxanes, fatty acid esters, as well as amine, alcohol, acid, ketone, ester, fluorinated and aromatic functionalized versions, physical blends and copolymers thereof of these polymeric resins. The polymeric resin may be present in an amount of about 5 wt% to about 95 wt%, or about 10 wt% to about 95 wt%, or about 20 wt% to about 85 wt%, or about 30 wt% to about 75 wt%, or about 40 wt% to about 65 wt%, or about 50 wt% to about 80 wt%, or about 10 wt% to about 20 wt%, relative to the total weight of the coating composition.

Suitable defoamers include, for example, mixtures of surfactants, tributyl phosphate, fatty acid polyoxyethylene esters plus fatty alcohols, fatty acid soaps, silicone emulsions and other silicone-containing compositions, waxes in mineral oil and inorganic particulates, blends of emulsified hydrocarbons, and other compounds commercially available as defoamers. Suitable coalescents include, for example, ester alcohols, hydrophilic glycol ethers, e.g.

Series of

DPM and

DPnB, hydrophobic glycol ethers, and block copolymers. Suitable dispersants include polyacrylates, such as ammonium polyacrylate salts,

Series, hydrophilic block copolymers, acrylic block copolymers and nonionic surfactants. Suitable rheology agents or thickeners include cellulose derived rheology modifiers such as microfibrillated cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose or mixtures thereof. Suitable non-cellulose derived rheology modifiers include one or more of emulsion copolymers, dicyandiamide, triols, polyoxyethylene ethers, urea, sulfated castor oil, polyvinylpyrrolidone, sodium alginate, xanthan gum and sodium silicate

In certain embodiments, the coating composition according to the present invention may comprise titanium dioxide in an amount of up to about 1.0 wt.%, or up to 0.8 wt.%, or up to 0.6 wt.%, or up to 0.4 wt.%, or up to 0.2 wt.%, or up to 0.1 wt.%, or up to 0.05 wt.%, based on the total weight of the coating composition.

The coating composition according to the invention is suitable for application on a range of articles or substrates. Suitable substrates include wood, plastic, metal. Methods for coating articles are known to those skilled in the art and include brushing and spraying.

In certain embodiments, the coating composition may have one or more of the following characteristics:

-good wet opacity;

-good dry opacity;

-good whiteness;

low yellowness

Good scrub resistance

Good resistance to soiling

Good uv protection;

avoiding the use of environmentally harmful and/or regulated compounds.

For the avoidance of doubt, the present application relates to the subject matter described in the following numbered paragraphs.

1. A coating composition comprising pigment particles, wherein the median particle diameter d of the pigment particles, measured by sedimentation using a Sedigraph₅₀From about 0.1 μm to about 5 μm, or from about 0.15 μm to about 5.0 μm, or from about 0.25 μm to about 4.5 μm, or from about 0.3 μm to about 4.0 μm, or from about 0.35 μm to about 3.5 μm, or from about 0.4 μm to about 3.0 μm, or from about 0.5 μm to about 2.5 μm, or from about 0.6 μm to about 2.0 μm, or from about 0.8 μm to about 1.5 μm, or from about 1.0 μm to about 5.0 μm, or from about 1.05 μm to about 4.5 μm, or from about 1.3 μm to about 4.0 μm, or from about 1.3 μm to about 3.5 μm, or from about 1.4 μm to about 3.0, or from about 1.4 μm to about 2.5 μm, or from about 1.3 μm to about 2.5 μm, and from about 0.2 μm to about 3.5 μm, or from about 2 μm to about 2.5 μm, and comprising pigment particles:

i) at least about 70% by weight zirconium dioxide;

ii) up to about 15 wt% silica;

iv) at least about 97% by weight of a combination of i), ii) and iii),

wherein the weight percent of zirconium dioxide of i) is the equivalent weight percent zirconium dioxide as determined by XRF; the weight percent of silica of ii) is the equivalent weight percent silica as determined by XRF; the weight percent of the one or more metal oxides of iii) is the weight percent of the equivalent weight of the one or more metal oxides as determined by XRF; and wherein the weight percentages of i), ii), iii) and iv) are each based on the total weight of the pigment particles.

2. A coating composition comprising pigment particles, wherein the median particle diameter d of the pigment particles, measured by sedimentation using Sedigraph₅₀From about 0.1 μm to about 1 μm, or from about 0.15 μm to about 1 μm, or from about 0.2 μm to about 0.8 μm, or from about 0.2 μm to about 0.6 μm, or from about 0.3 μm to about 0.5 μm, and the pigment particlesThe granule comprises:

i) at least about 70% by weight zirconium dioxide;

ii) up to about 15 wt% silica;

iv) at least about 97% by weight of a combination of i), ii) and iii),

wherein the percent by weight of zirconia of i) is the equivalent percent by weight of zirconia as determined by XRF; the weight percent of silica of ii) is the equivalent weight percent silica as determined by XRF; the weight percent of the one or more metal oxides of iii) is the weight percent of the equivalent weight of the one or more metal oxides as determined by XRF; and wherein the weight percentages of i), ii), iii) and iv) are each based on the total weight of the pigment particles.

3. The coating composition of numbered paragraphs 1 or 2, wherein at least a portion of the zirconium dioxide and at least a portion of the one or more metal oxides are present as a mixture in the pigment particles

4. The coating composition of numbered paragraphs 1-3, wherein at least a portion of the zirconium dioxide and at least a portion of the one or more metal oxides are present in the pigment particles as components of the metal oxide structure.

5. The coating composition of numbered paragraph 4, wherein the metal oxide structure is monoclinic, tetragonal, cubic or a mixture thereof.

6. The coating composition of paragraph 4 or paragraph 4, wherein the metal oxide structure is monoclinic and comprises at least about 97 wt% zirconium dioxide, as determined by XRF, based on the total weight of the pigment particles.

7. The coating composition of any one of the preceding numbered paragraphs, wherein the pigment particles comprise about 0.01 wt% to about 2.5 wt% hafnium oxide, based on the total weight of the pigment particles, as determined by XRF.

8. The coating composition of any of the preceding numbered paragraphs, wherein the pigment particles comprise from about 0.01 wt% to about 14.99 wt% yttrium dioxide, as determined by XRF, based on the total weight of the pigment particles.

9. The coating composition of any of the preceding numbered paragraphs, wherein the pigment particles comprise at least about 99 wt% of a combination of zirconium dioxide, silicon dioxide, and one or more metal oxides, as determined by XRF, based on the total weight of the pigment particles.

10. The coating composition of any one of the preceding numbered paragraphs, wherein the pigment particles comprise less than about 0.05 wt% iron oxide based on the total weight of the pigment particles as determined by XRF.

11. The coating composition of any of the preceding numbered paragraphs, wherein the pigment particles have a brightness of at least 85 measured according to ISO 2470-2.

12. The coating composition of any of the preceding numbered paragraphs, wherein the coating composition is measured at 8m according to ISO6504-3²Dry opacity/l is at least 95%.

13. The coating composition of any of the preceding numbered paragraphs, wherein the coating composition is at 8m as measured according to ISO6504-3 modified to omit the final drying step²The wet opacity is at least 75%.

14. The coating composition of any of the preceding numbered paragraphs, wherein the pigment particles are present in an amount of about 1 to 10 wt%, based on the total weight of the coating composition.

15. The coating composition of any of the preceding numbered paragraphs, further comprising one or more polymer resins, defoamers, crosslinkers, dispersants, coalescents, adhesion promoters, wetting agents, rheology agents, light stabilizers, and/or ultraviolet light absorbers.

16. The coating composition of any of the preceding numbered paragraphs, comprising titanium dioxide in an amount of about 1.0 wt% or less based on the total weight of the coating composition.

17. A method of making the coating composition of any of numbered paragraphs 1 to 15, comprising blending pigment particles with other components of the coating composition.

18. Use of the coating composition of any one of numbered paragraphs 1 to 15 to coat an article or substrate.

19. A method of coating an article or substrate comprising coating the article or substrate with the coating composition of any of numbered paragraphs 1 to 15.

20. An article or substrate coated with the coating composition of any of numbered paragraphs 1 to 15.

Examples

Pigment particles having the combination of components shown in table 1 were prepared and tested as described below.

Pigment samples a, k and l in Table 1 are monoclinic and they are obtained from zirconium oxychloride (ZrOCl) by calcination at 900 deg.C₂.8H₂O) by chemical precipitation. Samples a and k were jet milled and sample l was passed through an impact mill (coater mill) to obtain the respective particle sizes.

Pigment samples b, c and d use high purity molten ZrO₂Sample preparation: it was wet milled to form samples with three different particle sizes. The sample was then dried (110 ℃) and calcined at low temperature (450 ℃) to remove organic impurities. The resulting sample was then ground in the laboratory using a pestle and mortar.

Pigment sample h used high purity fused ZrO₂Sample preparation: it is wet milled, flocculated, dried (110 deg.C) and calcined at low temperature (450 deg.C) to remove organic impurities. The sample was then passed through an impact mill.

Pigment samples i and j use high purity molten ZrO₂Sample preparation: it was jet milled to form samples with different particle sizes.

Sample e is tetragonal spray-dried Zirconia from Zheijiang Zirconia Industry Co. (JK-3Y-ZN) containing about 3 mol% Y according to its technical data sheet₂O₃As a stabilizer.

Samples f and gMade by melting yttria and high purity monoclinic zirconia in an electric arc furnace at a temperature greater than 2800 ℃. For sample f, 5 wt% Y was used₂O₃And 95% ZrO₂For sample g, 13 wt% Y was used₂O₃And 87% by weight of ZrO₂. One 5 ton batch was made for each sample and the melt produced one large mass which was cooled to room temperature in one week. The solid molten material is separated from any unmelted material. The molten material is then crushed and ball milled. A slurry was prepared and wet bead milled to produce the final particle size. The slurry is then dried and calcined at low temperature (450 ℃) to remove organic impurities. Finally, the calcined material was passed through an impact mill.

Sample m was composed of lower purity molten ZrO₂Samples were prepared, wet-milled, dried, and then calcined at low temperature (450 ℃) to remove organic impurities. The resulting sample was passed through an impact mill.

Pigment particle samples a to k are according to the invention, and pigment samples l and m are comparative examples. For example, comparative example m contains 0.08 wt% iron oxide and has a low powder VIO, a low whiteness index and a high yellowness index compared to all the pigment particles according to the invention.

Preparation of the coating

The coating formulations according to table 2 were prepared using the following steps:

by reacting TiO with₂Pigment particles and/or ZrO₂Pigment particles and/or inorganic mineral extenders (e.g., calcined clay, PCC, talc, and/or GCC) are dispersed in a mixture comprising ammonia, Dispex a40 or Ecodis90P, Natrosol250HR, water, and optionally a biocide (activity MBS) and defoamer (Byk024) to make a mill-base to achieve about 60 wt% of target solids; DAC-150speedMixer was used for paint formulas A through E, and Dispermat CV2-SIP with a40 millimeter cowling blade (cowls blade) was used for paint formulas F through H; and

the millbase is put into the finished coating by adding a styrene acrylic binder (Acronal S790), a co-solvent (Texanol), a thickener (Acrysol TT935) and water.

ZrO of Table 1₂The pigment particles may be incorporated at 2 wt% or 4 wt% in the mill-base stage. In coating formulations F to H, ZrO₂Added in powder form. In coating formulations A through E, an equivalent amount of ZrO was mixed using 1.68 wt% sodium polyacrylate dispersant (DispexA40)₂The dry solids of the powder were pre-dispersed at 75 wt.% solids in a water-based slurry.

TABLE 2¹:

Coating formulation	A	B	C	D	E	F	G	H
									Pigment granules²	0	0.5	1	2	4	0	2	4
Calcined clay	12	11.875	11.75	11.5	11	13.69	13.11	12.55
									PCC	12	11.875	11.75	11.5	11	-	-	-
Talc	8	7.92	7.83	7.68	7.33	12.96	12.42	11.88
									GCC	16	15.83	15.66	15.32	14.67	11.04	10.58	10.12
Hydrous kaolin	-	-	-	-	-	8.40	8.05	7.70
									Perlite	-	-	-	-	-	1.92	1.84	1.76
Natrosol 250HR	0.4	0.4	0.4	0.4	0.4	0.23	0.23	0.23
									Dispex A40	0.7	0.7	0.7	0.7	0.7	-	-	-
Ecodis 90P	-	-	-	-	-	0.40	0.40	0.40
									Ammonia	0.05	0.05	0.05	0.05	0.05	0.05	0.05	0.05
Acticide MBS	-	-	-	-	-	0.10	0.10	0.10
									Byk 024	-	-	-	-	-	0.30	0.30	0.30
Acronal S790	11	11	11	11	11	11	11	11
									Texanol	1.4	1.4	1.4	1.4	1.4	1.4	1.4	1.4
Acrysol TT935	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45
									Water (W)	38	38	38	38	38	38	38	38
Coating% PVC³	77.8	77.8	77.7	77.5	77.1	78.2	77.9	77.4

¹All values except PVC are weight percent based on the total weight of the coating formulation.

²In the present example and comparative example, the coating composition B was used&The pigment particles of C being TiO₂Used in paint formulation D, E, G&Of H is ZrO₂

³Pigment volume concentration

The coatings were placed overnight at 23 ℃ and 50% RH in a controlled environment and then applied to Leneta card or Melinex (mylar) substrates at various thicknesses using a hand held or automatic draw down bar. The optical properties of the coating were then determined.

Wet and dry opacity at fixed spreading Rate

ISO6504-3 method "paint and varnish-determination of hiding power" was used to obtain a standardized measurement of dry opacity for each given coating film thickness or spreading ratio. The applied wet film per unit area was weighed, and then the opacity of the film after drying (dry opacity) was measured. Wet opacity was measured in a similar manner, where opacity was measured before the film was dried. The wet opacity was measured using an X-Rite spectrophotometer and the dry contrast or hiding powder (hiding powder) was measured using a Datacolor spectrophotometer.

The coatings were applied at five different wet film thicknesses (between 100 and 200 μm) on Leneta cards using a hand held draw down bar or an automatic bar using a Coatmaster 509MC Erichsen apparatus. The paint cards were weighed before and after the paint was applied and the area covered by the paint was measured. In m²Coating coverage in/l is calculated using the wet weight of the coating and its density. Wet opacity (100X Ryb/Ryw) was measured using an X-Rite apparatus 60 seconds after application. A polynomial function was applied to fit five measurements (thickness) of opacity to coating coverage, assuming 100% opacity at zero spread (infinite coating film thickness) to calculate at 8m²Wet opacity at a spreading rate (corresponding to a wet film thickness of 125 μm). After the paint film was dried, the dry opacity (100x Ryb/Rvw) was calculated from a polynomial fit of five measurements using the same method and measured using a Datacolor spectrophotometer.

Color after drying at fixed spreading Rate

The CIEL a b values of the dry coatings were measured on a white background of Leneta cards using the ISO6504-3 method as above and using a Datacolor mode600 spectrophotometer. Linear fit of whiteness L and yellowness index b to spreading rate can be calculated at 8m²L and b at a given spreading rate of/L.

The above measurements were performed on various coating formulations using the pigment particles of table 1 formulated according to table 2. The results of these measurements are shown in table 3. As also shown in table 3 below, it is,also prepares for using TiO₂Coating formulations were compared as pigment particles rather than the pigment particles of table 1.

Having a pigment particle diameter d as measured by Sedigraph shown in Table 3₅₀All examples a to k according to the invention provide coating compositions having better properties than paint formulations without pigments. For example, coating formulations according to the present invention provide significantly improved wet opacity. In each example, 8m²The wet opacity at/l is greater than 80. At the same time, good results are obtained in terms of dry opacity, whiteness and yellowness.

It was not possible to prepare coating compositions using the pigment particles according to comparative example l. Comparative example l has a larger particle size (Malvern d)₅₀Is 9.8; sedigraphd₅₀: not measurable) and not successfully incorporated into coating formulations. This attempt resulted in precipitation of the sample, so comparative example i was not suitable for inclusion in the coating formulation.

The coating formulation using comparative example m was not prepared because of poor properties, such as poor brightness and high yellowness.

Claims

1. A coating composition comprising pigment particles, wherein the median particle diameter d of the pigment particles, measured by sedimentation using a Sedigraph₅₀From about 0.1 μm to about 5 μm, and the pigment particles comprise:

i) at least about 70% by weight zirconium dioxide;

ii) up to about 15 wt% silica;

iv) at least about 97% by weight of a combination of i), ii) and iii),

2. The coating composition of claim 1, wherein at least a portion of the zirconium dioxide and at least a portion of the one or more metal oxides are present in the pigment particles as a mixture.

3. A coating composition according to claim 1 or 2, wherein at least a portion of the zirconium dioxide and at least a portion of the one or more metal oxides are present in the pigment particles as components of the metal oxide structure.

4. The coating composition of claim 3, wherein the metal oxide structure is monoclinic, tetragonal, cubic or a mixture thereof.

5. The coating composition of claim 3 or claim 4, wherein the metal oxide structure is monoclinic and comprises at least about 97% by weight of zirconium dioxide, as determined by XRF, based on the total weight of the pigment particles.

6. The coating composition of any one of the preceding claims, wherein the pigment particles comprise from about 0.01 wt% to about 2.5 wt% hafnium oxide, based on the total weight of the pigment particles, as determined by XRF.

7. A coating composition according to any one of the preceding claims, wherein the pigment particles comprise from about 0.01 to about 14.99 wt% yttrium dioxide, as determined by XRF, based on the total weight of the pigment particles.

8. A coating composition according to any one of the preceding claims, wherein the pigment particles comprise at least about 99 wt% of a combination of zirconium dioxide, silicon dioxide and the one or more metal oxides, as determined by XRF, based on the total weight of the pigment particles.

9. A coating composition according to any preceding claim, wherein the pigment particles comprise less than about 0.05 wt% iron oxide, as determined by XRF, based on the total weight of the pigment particles.

10. The coating composition of any one of the preceding claims, wherein the pigment particles are present in an amount of about 1 to 10 wt.%, based on the total weight of the coating composition.

11. The coating composition of any one of the preceding claims, further comprising one or more of a polymer resin, a defoamer, a crosslinker, a dispersant, a coalescent, a tackifier, a wetting agent, a rheology agent, a light stabilizer, and/or an ultraviolet absorber.

12. The coating composition of any one of the preceding claims, comprising about 1.0 wt.% or less of titanium dioxide, based on the total weight of the coating composition.

13. A method of preparing the coating composition of any one of claims 1 to 12, comprising blending the pigment particles with other components of the coating composition.

14. Use of the coating composition of any one of claims 1 to 12 for coating an article or substrate.

15. A method of coating an article or substrate comprising coating the article or substrate with the coating composition of any one of claims 1 to 12.